This V76 microphone preamplifier has up to 76 dB of gain. The original design combined a input pad with a gain switch, but this lacks flexibility and would not work well with a DI. This build splits the pad to a separate switch (matching the original impedance) and adds a DI for a line in. High pad attenuation allows use as a line amp.
The V76 is a four tube preamplifier, using the EF804S tube in the first three positions, followed by a EF80 driving the output. The preamp uses a clever input section design with switching feedback to achieve high gain with great frequency response. The noise performance is very good, at -120 dB.
The two plate chokes were wound by CJ (from groupdiy) to match the specs of the originals (250H and 400H) and I added steel shields, wrapped with adhesive backed mu-metal shielding to block magnetic coupling.
Using Jensen transformers for the input and output: a JT-115k-E90 transformer on the input and JT-10k61-1M on the output. The ?E90? designation means the Jensen has 90 dB of shielding.